1. Field of the Invention
The present invention relates generally to methods of sealing conduits in lateral well bores whereby the sealant can withstand stress induced conduit movements without failure.
2. Description of the Prior Art
Hydraulic cement compositions are commonly utilized in oil, gas and water well completion and remedial operations. For example, hydraulic cement compositions are used in primary cementing operations whereby a conduit such as a string of casing is cemented in a well bore. In performing primary cementing, a hydraulic cement composition is pumped into the annular space between the walls of the well bore and the exterior of a string of casing disposed therein. The cement composition is permitted to set in the annular space thereby forming an annular sheath of hardened substantially impermeable cement therein. The cement sheath physically supports and positions the casing in the well bore and bonds the casing to the walls of the well bore whereby the undesirable migration of fluids between zones or formations penetrated by the well bore is prevented.
The development of wells including one or more laterals to increase production has recently taken place. Such wells include vertical or deviated principal well bores having one or more laterally extending well bores connected thereto. Drilling and completion equipment has been developed which allows lateral well bores to be drilled from a principal well bore in which casing has previously been cemented. Each of the lateral well bores usually includes a conduit, known in the art as a liner, cemented therein which is tied into the conduit (casing) in the principal well bore.
While single lateral and multi-lateral wells have been successfully drilled and operated, a problem in the operation involves the cement utilized to bond and seal the conduits in the lateral well bores. Such conduits have been cemented in lateral well bores by introducing cement slurries into the annular clearances between the walls of the well bores and the conduits. The cement slurries set into hard masses to thereby support the conduits in the well bores and to seal the annuluses whereby fluid flow through the annuluses between formations and zones is prevented. Typically, the cement slurries which have been utilized set into brittle solid masses, and as a result, they cannot withstand the conduit movements caused by impacts and shocks subsequently generated by drilling and other well operations carried out in the laterals without cracking or shattering. Once the set cement is cracked or shattered, it allows leakage of fluid through at least portions of the well bores which is often highly detrimental.
Thus, there are needs for improved methods of sealing conduits in lateral well bores whereby the sealant can withstand stress induced conduit movements without failure.